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Ninjabyte ZPX-128 (universal Z80 computer kit)

Started by DarkestEx, January 13, 2016, 12:49:19 am

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DarkestEx

January 13, 2016, 12:49:19 am Last Edit: February 10, 2016, 01:20:44 am by DarkestEx
Hello!

Adekto and I were working on a new project that you fellow Z80 hackers should love:
A DIY Z80 computer kit that you can solder and more importantly hack into every aspect!

It will have 128KB of fine SRAM, VGA, mono audio, a 10 MHz Zilog Z84C00-10 processor, SD card interface for loading the kernel and for accessing files from the Z80, PS/2 for attaching a keyboard and a fancy LED indicator.

c4ooo

I have tried doing that, here is the project ATM:

Anyhow, since this is closer to me then ARM, i would love to contribute as a programmer!   :D

DarkestEx

Making steady progress. Almost all part footprints and pinouts are created now in Fritzing and a good part of the schematic is done.


DarkestEx

Well actually it is pretty different from that one, stay tuned :)

We made a lot more progress with the schematics. I worked a lot on the interface between z80 and PXA. It consists of 3 74HC299 universal high-speed CMOS shift registers.
The reat is done with a MCP GPIO expander and some good old 74 series glue logic.

DJ Omnimaga

January 22, 2016, 05:56:10 am #5 Last Edit: January 22, 2016, 05:59:02 am by DJ Omnimaga
Have you bought all parts needed for this project yet? And do you think you could manage to work on this project alone? Because to be honest, due to what happened with Microcat I probably won't get my hopes up on this project until you have purchased all the parts (in case you run out of money once again) and showed us that you can continue working on this even if all other teamates stop doing anything (this is why I never work on team projects). But if it succeeds then I will be happy because that would be a nice thing to mess around with, plus it has a Z80 in it. :)

DarkestEx

Quote from: DJ Omnimaga on January 22, 2016, 05:56:10 am
Have you bought all parts needed for this project yet? And do you think you could manage to work on this project alone? Because to be honest, due to what happened with Microcat I probably won't get my hopes up on this project until you have purchased all the parts (in case you run out of money once again) and showed us that you can continue working on this even if all other teamates stop doing anything (this is why I never work on team projects). But if it succeeds then I will be happy because that would be a nice thing to mess around with, plus it has a Z80 in it. :)

Yes, i started the project alone and can finish it alone if others lack the time to help. Though I really hope c4ooo can help every here and then. Thank you!

Yes, I bought most of the parts already a while back. I still need to get some when the schematic is done. For the Microcat, I had bought all parts, that was not the problem, but making a prototype PCB. I wouldn't have been able to solder it myself and it would have been expensive to make just a single one for testing.

This project should work a lot better and is probably way more interesting for all of the z80 fans here :)

DJ Omnimaga

That's good, then. And for the Microcat prototype, couldn't you just have re-used the parts you already had? Or were they exclusively made for use on a breadboard?


As for the Z80 I wouldn't say the project is 100% pure Z80 since another CPU does a lot of work for display and stuff, but if it's still Z80 enough to be programmed like the ZX Spectrum and Z80 calcs, then I always wondered if it could run KnightOS or some sort of firmware that could run old calculator programs? Not that it's the priority right now, but that was something I was wondering.

DarkestEx

Quote from: DJ Omnimaga on January 22, 2016, 08:28:07 am
That's good, then. And for the Microcat prototype, couldn't you just have re-used the parts you already had? Or were they exclusively made for use on a breadboard?


As for the Z80 I wouldn't say the project is 100% pure Z80 since another CPU does a lot of work for display and stuff, but if it's still Z80 enough to be programmed like the ZX Spectrum and Z80 calcs, then I always wondered if it could run KnightOS or some sort of firmware that could run old calculator programs? Not that it's the priority right now, but that was something I was wondering.

No, it was never really the parts. The PCB was the problem. First, KiCad just sucks and I have not really much experience with multilayer PCBs. Even double layer ones are quite hard to do correctly.
Then, making one PCB would cost around 80€ (without the required solder mask it would've been around 60.
Making one mistake would have required making the changes to a file and then ordering a new board. And all parts too. Also soldering would have been a big problem.

About KnightOS, cumred said that it would probably work and that he could eventually port it if he has time.

c4ooo

The current problem with porting KOS is that the hardware that is being emulated around the z80 is nothing like the hardware on the ti84 ;) Obviously one can program an OS with the same shell, but the kernel will have to be mostly rewritten probably :/ Right now Darkest wants an old school textbased shell, while i want a slighly more advanced shell with a semi graphical UI <_< Obviously there is nothing wrong with making a semi graphical UI that has a built in command prompt.  :)

DJ Omnimaga

It probably depends if KOS mostly use the Z80 instructions set, right? Wouldn't Z80 ASM on the ZPX-128 be mostly different when it comes to drawing stuff to the screen? (Since it seems like video stuff is done by a different processor)

The biggest issue with KOS from what I heard would be copyrights, because I heard (and saw) that the author is very strict about re-use of his intellectual property (per open-source standards, at least) and you have to make sure he is credited properly. Make sure to read the license thoroughly before releasing new versions or ports of KnightOS, let alone selling hardware on which it runs.

DarkestEx

Quote from: DJ Omnimaga on January 28, 2016, 08:21:39 am
It probably depends if KOS mostly use the Z80 instructions set, right? Wouldn't Z80 ASM on the ZPX-128 be mostly different when it comes to drawing stuff to the screen? (Since it seems like video stuff is done by a different processor)

The biggest issue with KOS from what I heard would be copyrights, because I heard (and saw) that the author is very strict about re-use of his intellectual property (per open-source standards, at least) and you have to make sure he is credited properly. Make sure to read the license thoroughly before releasing new versions or ports of KnightOS, let alone selling hardware on which it runs.

Well, the assembly language itself is completely the same, but KOS is incompatible with the ZPX-128 as it has entirely different hardware. So doing certain things is entirely different on the ZPX-128 than it is with a TI calculator.

About the licence, he hasn't said anything negative, but it wouldn't run anyways. We will do our own OS anyways.

DJ Omnimaga

Ah I see. I didn't realize the OS relied this much on the hardware. A new OS is better, then.

c4ooo

So... we ran into a problem. The previous system controller chip we where going to use was not good enough. Apparently it had too little ram. This chip also runs programs from ram, leaving us with too little ram. I have suggested using a Atmel ATSAM3X8E chip, which is the chip used in the Arduino duo and also pretty good for the tasks we want. Unfortunately, the Atmel SAM3X8E only come with SMD pins, which unlike DIP is hard to solder onto a board. Darkest talked about a third chip, but i dont know if it is good enough <_< :( D:

DJ Omnimaga

That sucks. I hope you can find a workaround that isn't too expensive :(

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